Telephone and circuits therefor.



No. 887,998. PATENTED MAY 19, 1908.

E. B. CLEMENT.

TELEPHONE AND CIRCUITS THEREFOR. APPLICATION FILED JUNE 20,1903.

2 SHEETSSHEET 1.

No. 887,998. PATBNTED MAY 19, 1908. B. B. CLEMENT.

TELEPHONE AND CIRCUITS THEREFOR.

APPLIGATION FILED J NE 20,1903.

2 SHEETS-SHEET 2.

UNITED STATES PATENT .OhFICE.

EDWARD E. OLEM ENT, OF WASHINGTON, DISTRICT OF COLUMBIA.

TELEPHONE AND CIRCUITS THEREFOR.

To all whom it' ma y. concern:

Be it known that I, EDWARD E. CLEMENT, a citizen of the United- States, residing in Washington, District of Columbia, have invented a new and useful Telephone and .Cir-

cuits Therefor, of which'the following is a specification.

My invention relates to telephoneinstruments, and'the circuits interconnecting the same, and is particularly concerned with such instruments and circuits as are used in common battery systems.

It has for its object the improvement of both instruments and circuits to produce in creased' efliciency and decreased ex ense of production and maintenance, and w 'le it. is principally applicable to the subscribers station ap aratus, it will be sufficiently apparent from t e detailed description hereinafter given that it may also be applied to portions of the central station equipment.

i In common battery systems the current supplied for the subscribers transmitters, as we as for signaling, is derived from the central station where is located a suitable source, usually a secondary battery. As metallic circuits are now exclusively prescribed by the rules of good practice, and as the transmitter in many cases has to vary directly the resistance of'a circuit, comprising the line wires and a portion of theconnections at central,

as well as its own contacts and its correlated receiving apparatus, it has been found advantageous to raise the voltage of the current supply, until at present 50 volts has come to be regarded as the standard. Before this .raising of the voltage, however, .the problem of how best to connect the receivers in circuit had already been considered, and two cludedin one path conductively discontinu-- ous and inductively continuous by reason of the inclusion of .a condenser, the battery current taking the other path, and the transmitter as before being, directl in the c rcuit. Some modifications of t ese ar; 4,

Specification of Letters Patent.

Application filed June 20; 1903. Serial N'o. 162,338.

Patented May 19, 1908.

r'angementshave been worked out and used, wherein the transmitter forms a part of an inductively complete local circuit including the primary winding of an induction coil whose secondary is to'line, the line having current supply branches to the local transmitter circuit. Such an arrangement is really a combination of both the others, the transmitter beingassociated with the induction coil instead of the receiver. these arrangements is objectionable principally on account of the losses in the induction coil, which impair the efficiency of receiving,

materially. The second arrangement is ob:

jectionable because of the condenser, which 1s expensive and liable to derangement and is also bulky. In the modified condenser arrangement employing a transmitter induction coil, the efficiency of transmission'is high, but it has been found that this is not due to the condenser, as if-the receiver and condenser branch is broken transmission remams excellent. In order to avoid the use of either of these some of the operating companies have limited themselves to the primal arrangement wherefrom all telephony has sprung, viz. that in which the receiver and transmitter are both included directly in the line. In such case it is well if the voltage is raised substantially, for the resistance'of the receiver windings is a considerable part of the entire resistance of the circuit; but on the other hand, the hi her the voltage and the more current thereby'forced through the receiver windings to the transmitter, the greater the risk of depolarizing the receiver magnet or of buckling its diaphragm, or both.

By the use of my present invention I am enabled to dispense with the condensers or receiver induction coils, include the receiver directly in the'line with'the' transmitter, reduce the resistance of its windings to onehalf that usually employed, prevent any magnetic effect on its pole pieces by direct current, and for alternating currents or voice .currents to maintain its eiliciency at a very high percentage.

My invention consists essentially in placing two equal and opposite windings on the receiver poles, connected in parallel to the receiver terminals-,the branch containing one winding being caused to present a high ,im-

edance to alternating or voice currents, both branches being otherwise balanced. The windings may be twin, that is laid on together and in parallel throughout ou one The first of spool, in which case a separate impedance .coil is included in series with one of them; or

s ools slipped on they may be on separate the magnet poles end to en in which case I preferably make the, coil farthest from the end of the pole of high impedance, as by giving it more turns and surrounding it with a complete magnetic .circuit, in which case no separate coil is needed, and the other winding on the pole piece, being nearest to its extremity, has the greatest efficiency in producing effects on the diaphragm.

My invention is illustrated in the accompanying drawings, in which Figure l is a diagram showing two subscribers stations connected together, with a common source of energy, and the simplest mode of connecting the apparatus. Fig. 2

" is a diagram showing a single pole receiver wound and connected at the subscribers station accordin to my invention. Fig. 8 is a diagram similar to Fig. 2, showing the arrangements and connections of a bi-polar receiver. Fig. 4. 1s a sectional view of a single pole receiver embodying my invention, the

magnet structure being shown in full lines,

and Figs. 5 and 6 are similar views to Fig. 4, showing the mechanical construction and arrangement of a bipolar receiver, the shell being removed in each case.

Referring to the drawings, in Fig. 1, 12 and 34 are theline wires leading to two subscribers stations A and B, respectively. At station A, transmitter T and receiver R are included directly in-the line circuit, and at station B, transmitter T and receiver R are likewise connected directly in the line circuit. At an intermediate point a talking battery M is bridged across the united circuits along with an impedance coil If The current from this battery flows in both directions and supplies both substation transmitters, by the operation of which 1 electrical waves are caused to pass in one direction or the other to affect the respective receivers, being choked out of the battery bridge by the nnpedance coil. This simple arrangement would be excellent in practice if the relation between the battery potential and the line resistances be such as to furnish a sufficient current flow and if this current flow did not injuriously affect the receiver. In attaining the necessary current flowit is desirable to keep the resistance of the receiver low, and yet in order to make it efiicient for voice Waves it should be wound with a sufficient number of turns to make its resistance What high. l a

From the above diagram and the remarks made on the subject,' the problem to be solved will have been rendered lain. It is this: to put the receiver in the line with the transmitter, as in Fig. 1, and yet keep the line resistance down and revent the battery current from either depo arizing the receiver somemagnets or buckling the diaphragm. My

solution ofthis problem is illustrated in Figs. 2 to 6.

Referring to Fig. 2, R is the receiver and T is the transmitter, as before. The transmitter is included directly in the line 1-2, but the receiver is included therein by means of two parallel branches 6 and 7. The receiver has a permanent magnet-structure p and a soft iron pole-piece r upon which are WOilIld the 0 posing 00118 1 and r, connected 'mately the standard number. of turns and resistance. Now, suppose direct current coming from central to traverse line-wire 1, pass through the coils r and r in parallel and oppositely, the branches 6 and 7 in parallel, and the coil I and resistance 'i in parallel, the magnetic efiects due to. r and 1* will be equal and. opposite, andtherefore their resultant will be zero, leaving the pole-piece r unaffected, except by the permanent magnet; Suppose, however, that voice waves or alternating currents come over the circuits. Branch 6 will be ractically impassable for them because. of t e high coeflicient of selfinduction of the coil I They will therefore traverse the branch 7and'coil rproducing thereby substantially the same effect that they would in an ordinary receiver. Any slight leakage through the branch 6 would notaffect-the efficiency of the instrument through coil 1", because as the coil 1" is nearest the pole end, and as the coils are end on, any neutralizing effect would be infinitesimal. It is to benoted in this arrangement that for battery currents or direct currents the resistance of the receiver is divided by two, which is a long step toward raising the efficiency of transmission.

Referring now to Fig. 4, the usual rubber shell 8 with cap 8 is shown in section, containing the magnetic structure 1), its polepiece and windings. The instrument shown is a single ole receiver the same as in 2, anda sing e soft iron pole-piece r is shown provided with the two op ositely wound coils r and r. Instead of maliing a separateimpedance coil to choke out the voice waves from one of these windings, I refer to construct the coil 1' so that it wi have a very high coefiicient of self-induction. This I accomplish by inclosing it in a soft iron jacket so as to give it a closed magnetic circurt. I may also give it a greater number of ing one pair, and r and r" the other.

for direct current.

turns with a correspondingly increased re A convenient form of acket sistance. comprises the punched out soft iron heads 19 -1) and the tight fitting ring or sleeve p compressed thereon. Sufiicient iron should be employed in this. magnetic circuit to in sure a high retardation, and if desired bothv but with a double pole-receiver connected up instead of the single pole receiver. The horseshoe magnet p has soft iron pole-pieces r, 1', which carry opposed windings, lettered 1*, r", '1 1', respectively, r and r constitut- These respective coils, and the respective airs, oppose each other in their magnetic e ects, The impedance coil'I being included in branch 6, however, chokes lies in front of the pole I thus brin continuityi so other, because thus a wider air all voice currents into the other branch 7.

The mechanical construction of the biolar receiver is shown in Figs. 5 and 6. ere p is the permanent magnet, carrying soft iron pole-pieces r and r Between the limbs of the magnet a block of insulation g is fitted with the binding screws 9 to which the ends of the cord Q are led. The polepieces carry the windings r 7* 1' and r", as shown in Fig. '3, 1' and 1" being next to the ends of the pole-pieces. Each coil, 1* and r has a closed magnetic circuit comprising the core and a built up or laminated ring of soft iron whose members p, p are in close contact with the cores, and are connected by side members 19 Between the ends of the magnet-limbs a distance piece or block 11 preferably'of nonmagnetic material, such its ends threaded for the urpose of screwing into the rubber shell, which is not shown, in a well understood manner. The diaphragm ieces as usual, and the connecting wires 9 g' to which the pairs of coils are connected in parallel, pass to the screws g there making connection with the cord conductors.

Thereason I prefernot to incase each coil ofmybi-polar receiver entirely in iron is that the magnetic circuit too near to etween the coils, and'I prefer to use the iron rings shown, set flatwise to each gap is maintained between the coils, 'and the lines. ,of

force through the diaphragm are not de-- creased.

While I have described my improved reas lead or brass, has

ceiver as used in connection with common battery circuits, I wish it to be understood that it is equally efiicient, and may be useful, in circuits of all types. Its cost is but a trifle more than that of the ordinary receiver,

its efficiency is quite as high, and it can be used as a standard article on-alllines with equal success.

I do not wish to limit myself to the specific mechanical construction shown, but wish it to be fully understood that I am well-aware of many variations that might be made without de arting from the spirit of my invention. I believe I am the first to successfully produce a metallic circuit wherein a receivermay be included directly, being neutral for continuous currents but active for alternatingvcurrents.

hen my arrangement is employed in' common battery systems a very important advantage attained is the total or'substantial absence of the sharp clicks-due to the making and breaking of battery circuits in making connections. Even Where there is self induction in.the circuit the clicks are reduced to the faintest sounds possible.

I do not intend'to abandonany of the matters-canceled herefroin, but shall file a divisional application covering the same.

Having thus described my invention, what I claim, and desire to secure by Letters Patent of the United States is 1. In a telephone exchange system, a central ofiice, a p ing therefrom to substations, a common source of direct current supplying energy over said lines to the substations, and means at each substation to utilize said energy comprising the following instrumentalities: a i

pair of parallel bridges across the line, a transmitter connected in-series with the line and both bridges, a receiver having a pern anent magnet and an elongated iron olepiece thereon with two differential win ings on the po1e'-p1ece,one of said windings being nearer the end of the pole than the other and urality of line circuits extendhaving itsmagnetic circuit passing through. the diaphragm of the receiver only, while the other winding-has such an arrangement of its coils and magnetic circuit as will ofier impedance to alternating currents. I

2. In a telephone system, a pair of subscribers stations connected to ether for conversation, a common battery ridged; across the connected lines to sup ly current to them both, means to prevent eakageof voice currents through the battery br1dge, and' means at each substation to utilize the batteryj current comprising the following elements: a pair of parallel bridges across the line, a transmitter connected iii series withthe line and both bridges, a, receiver having a permanent magnet and an elon ated iron" po piece thereonwith two, iflerential windingson the pole-piece, one of said Win'dings being nearer the end ofthe pole than the my name in the presence of two subscribingother and having its magnetic clrcu'it passing wltnesses.

through. the diaphragm of the receiver only,

while" the other Winding has an iron returncircuit for its lines of force whereby it will offer high impedance to alternating currents.

- Inwitness whereof, I haveherennto signed EDWARD CLEMENT.- Witnesses FRANK D'. ORME, FLORA RAYMON 

